Adler was born in Queens, New York on January 17, 1986. A year after Adler was born, his family relocated to Scottsdale, Arizona. He attended Horizon High School, and immediately after graduating in 2004, he moved to Los Angeles to pursue a career in acting. After various roles in a number of productions, Adler was cast in a minor day player role in the Fox television series Glee as school jock and bully Dave Karofsky. Glee creator Ryan Murphy was impressed with his performance and started to write more for him. In the November 2010 episode "Never Been Kissed", written to tackle the issue of LGBT youth bullying, Karofsky is revealed to be a closeted gay teen. He received positive responses via the social networking websites Twitter, Tumblr and Facebook, and commented that he was "honored to represent such a large group of people". The character eventually gives up his bullying and makes his peace with Kurt, but he remains closeted. Adler has been praised for his performance in episode 3x14, "On My Way", during which after his character is outed, he attempts suicide. He recently completed starring in Dylan Baker’s independent film “23 Blast,” opposite Stephen Lang, about a football star who’s suddenly stricken with irreversible blindness. Additionally, he has two movies in the can and scheduled to be released later this year - the action/drama “AWOL,” a Vietnam-era story about a soldier who quits his post to find the girl who left him, co-starring with Liam Hemsworth and Teresa Palmer, and the horror/comedy “Detention of the Dead” about a group of high school misfits who are trapped with classmates that have turned into zombies (which is currently playing the Festival route around the world). For television, Adler just completed work on Shawn Ryan’s new action drama for ABC, “Last Resort,” opposite Andre Braugher and Scott Speedman,Adler is also heavily involved with activism. Following the Glee episode "Never Been Kissed", Adler was contacted by the It Gets Better Project, an internet based project founded by Dan Savage and his husband, Terry Miller, which aims to prevent suicide among LGBT youth. Adler recorded a heartfelt video for the project, offering words of hope and encouragement for kids and teens facing bullying due to their sexual orientation. On November 15, 2010, Adler spoke at the Anti-Defamation League’s Concert Against Hate at the Kennedy Center in Washington, D.C. Adler has also worked closely with the Muscular Dystrophy Association to help raise awareness of the hereditary muscle diseases. Adler's mother and grandmother have both passed from Facioscapulohumeral muscular dystrophy, also known as FSH or FSHD.